Researchers from Cologne University sent 96 people to watch a movie, giving half of them popcorn. Prior to the start of the movie, ads for products with which the audience was not familiar were shown. When questioned a week later, moviegoers who ate the popcorn did not show a preference for the products in the ads, while those who didn’t consumer popcorn did, the BBC notes.

“The mundane activity of eating popcorn made participants immune to the pervasive effects of advertising,” one of the researchers commented, noting that the results could convince advertisers to try and ban popcorn from theaters.

That could provoke resistance from theater owners, who generate substantial revenue from concession stand sales.

The study was recently published in the Journal of Consumer Psychology. The researchers speculate that the act of chewing can disrupt people’s “internal speech,” which helps them remember brand names.